In EP 344 183 B1 has been described an actuator in the form of a positive-fit shaft coupling in which a quick engagement and disengagement of two shaft parts is made possible by the fact that at least one of the two coupling halves is equipped with drivers which engage in recesses of the other coupling half or of a part connected therewith and the relative position of the drivers can be changed to two shift positions so that different rotational angles can be adjusted between the shaft parts to be coupled. The coupling halves have distributed on the periphery drivers in the form of driver bolts which carry rollers. The latter engage in recesses designed as guide grooves of a coupling sleeve.
Disadvantageous in the prior art such as described in EP 344 183 B1 is the fact that due to the design principle with the drivers distributed on the periphery, a larger radial installation space is needed which, in the first place, limits the ground clearance in off-road vehicles and that, due to the multiplicity of small structural parts, the resulting high sensitivity to soiling can impair operation.
The problem on which this invention is based is to show an actuator which, because of its small radial extension, does not limit the ground clearance of motor vehicles and yet can transmit strong torques and allow firm teeth settings.
This problem is solved by a generic actuator incorporating the present invention.
Because of the compact design mainly in radial direction and reduced number of structural parts susceptible to failure and sensitive to soiling, the actuator, according to the invention, is particularly adequate for installation in vehicles used in difficult grounds. By integrating the driver and prestressed springs in a housing, it is possible to reduce installation space and the multiplicity of structural parts.
An annular coupling element with an internal driver preferably designed as internal tooth forms a housing bottom and is connected with a stabilizer. A second annular coupling element has an external driver connected with one other stabilizer. A third coupling element is preferably designed as an axially displaceable piston with teeth contours adapted to the two other coupling elements. By the interaction of the three coupling parts, a very stable construction can be shown on small installation space. The coupling splines of the individual coupling elements can be adapted to the particular utilization. They can be designed, e.g. as teeth or shaft/hub connections. Besides, the effective torsional length of the actuator is not limited by the compact design. This is made possible primarily by a stabilizer that passes through the actuator. To avoid an expensive surface machining of the stabilizer and makes an optimum service life of the structural part possible, a housing cover can be connected with the stabilizer by a low-friction bearing bush. The low-friction bearing bush is secured on rods. An expensive machining of the stabilizer can thus be eliminated. In the coupling element designed as piston, an end cutoff can be integrated which can work mechanically, electrically, or hydraulically. Besides, a valve function can be integrated in the coupling element designed as piston.